First, the first aspect of the present invention is described.
Normally, manufacturing methods for a ceramic sinter in which particles or crystals are oriented are largely divided into the following two methods.
(1) A method whereby ceramic particles with anisotropic shapes are oriented within a molded article, and thereafter sintered.
With this method, a doctor blade process, an extrusion molding process, or another process is used to orient ceramic particles with anisotropic shapes within a molded article. Recently, attempts have been made to use the crystalline magnetic anisotropy within a substance to orient crystals within a molded article by imposing a magnetic field during molding. Thus, a ceramic sinter in which the particles or crystals are oriented can be manufactured by sintering, in the atmosphere or a specific environment, a molded article in which the particles and crystals are oriented in advance.
(2) A method whereby a ceramic molded article with anisotropic crystals is heated or sintered while pressure is applied from one or two directions.
Representative examples of this method include hot-press sintering, forge-sintering, and sinter-forging. All of these methods are methods for heating or sintering while imposing a mechanical pressure load from one or two directions on a molded article or a sinter that contains large anisotropic crystals or ceramic particles with anisotropic shapes, and oriented materials can be easily manufactured thereby.
In both cases of hot-press sintering and forge-sintering, a die containing a raw material powder is placed in a furnace and heated while mechanical pressure is applied, or pressure is applied after a predetermined temperature is reached.
In common practice, sinter-forging is a method in which a molded article that contains large anisotropic crystals or ceramic particles with anisotropic shapes is sintered, and mechanical pressure is then applied from one direction to obtain an oriented material. It is known that when the mechanical load pressure is high the degree of particle or crystal orientation is also high.
Next, conventional manufacturing methods for inorganic films can be largely divided into liquid-phase methods and gas-phase methods because the starting raw material is commonly different.
The sol-gel process is a representative technique of liquid-phase methods. This method is a method for obtaining an inorganic film by admixing an alkoxide or the like so as to achieve a prescribed composition, applying the resulting mixed solution to a single crystal substrate composed of Si, SrTiO3, or the like, and heat-processing this in an electric furnace. With such sol-gel processes, an inorganic film in which the particles or crystals are oriented and which possesses a lattice constant that is approximate to or equal to the lattice constant of the desired ceramic film can be obtained by way of nucleation and epitaxial growth on the substrate through the use of a single crystal substrate that possesses strong crystal orientation in one direction. Technology for manufacturing film with pronounced crystal orientation by using single crystal particles as seed particles, aligning the crystal directions in advance, and mounting the crystals on a substrate has recently been reported.
The following drawbacks result from the normal manufacturing methods described above in the manufacture of an inorganic film and a ceramic sinter in which pronounced particles or crystals are oriented. The term “pronounced particles or crystals are oriented” refers to the case in which the ratio of oriented particles or crystals is considerable with respect to the desired particles or crystals.
(1) The doctor blade process is a technique that is normally carried out by forming a slurry comprising solvents, plasticizers, binders, or other additives, allowing the slurry to flow from a knife edge called a doctor, receiving the slurry onto a carrier film, and moving the film while drying to fabricate a ceramic sheet with a thickness of several tens to 100 μm. A ceramic molded article is fabricated by laminating 10 to 100 sheets of the resulting ceramic sheet and removing the binder contained in the resulting laminated article. With this method, because the particles with anisotropic shapes become oriented when they flow from the knife edge, it is important to reduce the thickness of the ceramic sheet in order to achieve pronounced orientation within the molded article. As a result, the method has a drawback in that the number of laminated sheets must be greatly increased in order to obtain a thick laminated molded article. The manufacturing processing steps of this method are lengthy, fabrication requires a considerable amount of time, and highly trained personnel is needed to manufacture a sheet without defects, in addition to other drawbacks.
(2) The extrusion molding process extrudes a plasticized ceramic base comprising powders, solvents, plasticizers, binders, and other additives into a die having a prescribed shape with the aid of a screw or another means to fabricate a molded article. At this time, particles with needle shapes, rod shapes, disc shapes, plate shapes, or other anisotropic shapes are oriented in parallel to the extrusion direction. However, this has drawbacks in that large differences in the degree of particle orientation occur on the surface of the extruded molded article and in its interior, and distortion in the shape of the sinter, cracking-induced breakage, swelling, and other defects easily occur during heating or sintering.
(3) The crystal orientation technique that makes use of the magnetic anisotropy of the crystals in a material is determined by the applied magnetic force due to the orientation and degree of magnetic anisotropy of the crystal axis. As a result orienting a crystal may be difficult for some materials when the magnetic anisotropy of the crystal axis is small or when the magnetic flux for generating a magnetic field is small. A magnetic field generator is expensive, and is not suitable as production equipment for common use because expenses are incurred for maintenance and safety management.
(4) Hot-press sintering, forge-sintering, sinter-forging, and other methods are processing technologies that are capable of orienting particles and crystals within a ceramic sinter during baking, but all these methods have drawbacks in that they require that pressure be applied to a sample with the aid of a push rod or a mold die, so the contact material surface becomes soiled and byproducts based on the soiling are easily generated. As a result, the surface of the sample must be polished or ground after baking, and manufacturing costs are increased. Also, considering the polishing or grinding after baking, these methods have drawbacks in that they cannot be applied to manufacturing oriented films comprising a thin film with a thickness of only several tens of micrometers to several millimeters.
The first aspect of the present invention was contrived to solve the drawbacks described above, and provides a method for manufacturing a ceramic sinter and an inorganic film that does not require a special skill, a magnetic generator or other special device, or processing after grinding, and by which the surface and the center portion of particles or crystals are oriented with a uniform orientation by means of a simple operation, and further provides a ceramic sinter and an inorganic film.
Next, the second aspect of the present invention is described.
Bonding different types of materials or bonding materials of the same type is an important technology from the standpoint of endowing base samples with new functions, bringing together or compounding material functions, and improving thermal resistance and thermal shock characteristics. Normally, bonding different types of materials or bonding materials of the same type involves the adoption of either (1) a method for inserting an intermediate material between materials, or (2) a method for applying mechanical pressure to a material to be bonded. Of these methods, method (1) uses as a bonding material a material that normally forms a liquid phase at a low melting point or softens at a low temperature. Furthermore, stress-alleviating material is sandwiched and bonded between the materials to be bonded in order to alleviate stress that is generated by the difference in thermal expansion of the materials.
However, when this type of bonding material and stress-alleviating material is used, problems occur in that the bonding step becomes complicated, the bonding material or the stress-alleviating material portion becomes a source of breakage, and so on. A lead-based material is used in large quantities as the low-melting bonding material, but from the standpoint of water pollution, environmental pollution, and sanitary considerations, the use of lead-based materials has been restricted in recent years. Next, bonding is carried out through the use of a hot-press sintering device, a crimping device, or another device when materials that having a thickness of several centimeters or more are bonded with the methods described in (2) above. In this case, there are advantages in that bonding materials and stress-alleviating materials can be dispensed with, but the drawbacks include the fact that the size of the sample that can be bonded is limited by the size of the hot press push rod, a processing and removal step is required because the contact surface with the push rod becomes soiled, the thickness of the material to be bonded is limited, and bonding a material to the surface of a sample with a complex shape is difficult.
The second aspect of the present invention was contrived to solve the drawbacks described above, and provides a method for tenaciously bonding a material to the surface of the base sample, and provides a product thereof.